The disclosure provides a method and system for optimizing production of a natural gas liquefaction process, the method comprising the steps of: selecting at least one manipulated variable (MV) for controlling the liquefaction process; selecting at least one control variable (CV), the at least one control variable at least comprising liquefied natural gas (LNG) throughput; providing at least one model, each model providing a dependency of the at least one control variable (CV) on the at least one manipulated variable (MV); using the at least one model to estimate LNG throughput for at least one of the manipulated variables (MV); obtaining process data from the liquefaction process, the process data at least including observed values of LNG throughput; creating a gain matrix based on said interdependencies; and using the gain matrix to optimize a process control system of the liquefaction process.

A liquefaction system is capable of sequentially or simultaneously liquefying multiple feed streams of hydrocarbons having different normal bubble points with minimal flash. The liquefying heat exchanger has separate circuits for handling multiple feed streams. The feed stream with the lowest normal boiling point is sub-cooled sufficiently to suppress most of the flash. Feed streams with relatively high normal boiling points are cooled to substantially the same temperature, then blended with bypass streams to maintain each product near its normal bubble point. The system can also liquefy one stream at a time by using a dedicated circuit or by allocating the same feed to multiple circuits.

The present disclosure designs a mixed refrigerant hydrogen liquefaction device including a normal-pressure precooling cold box, a vacuum cryogenic cold box, a hydrogen refrigeration cycle compressor unit, a nitrogen cycle refrigeration unit and a mixed refrigerant cycle refrigeration unit. The precooling section uses a mixed refrigerant process and a nitrogen cycle refrigeration process as the main sources of cold energy. The refrigerant refrigeration cycle is the main source of cold energy in the temperature range of 303K to 113K. The liquid nitrogen refrigeration cycle is the main source of cold energy in the temperature range of 130K to 80K. The hydrogen refrigeration cycle provides cold energy for the temperature range of 80K to 20K. Most of the BOG generated in a storage part is recovered by an ejector. A plate-fin heat exchanger is filled with ortho-para hydrogen conversion catalysts to realize the para hydrogen content of liquefied hydrogen ≥98%.

A main heat exchanger receives and partially condenses an effluent fluid stream so that a mixed phase effluent stream is formed. A primary separation device receives and separates the mixed phase effluent stream into a primary vapor stream including hydrogen and a primary liquid stream including an olefinic hydrocarbon. The main heat exchanger receives and warms at least a portion of the primary vapor stream to provide refrigeration for partially condensing the effluent fluid stream. The main heat exchanger also receives, warms and partially vaporizes the primary liquid stream. A mixed refrigerant compression system also provides refrigeration in the main heat exchanger.

A cooling system includes a compressor configured to pressurize carbon dioxide to form pressurized carbon dioxide, a mixer configured to generate mixed refrigerant in which the pressurized carbon dioxide and solvent in a liquid state, a depressurization apparatus provided downstream from the mixer and configured to depressurize the mixed refrigerant, a separator configured to separate carbon dioxide in a gas state from the mixed refrigerant, a heat exchanger configured to exchange heat between the mixed refrigerant cooled through depressurization and a fluid to be cooled, and a second heat exchanger configured to cool the carbon dioxide or the mixed refrigerant using vaporized carbon dioxide or the mixed refrigerant.

A method for determining an operating condition of a liquefied natural gas plant (2) includes preparing a training model (88) generated by machine learning using training data in which operating conditions data including a composition of a feed gas, a composition of a mixed refrigerant, and an ambient temperature and operation result data including a production efficiency of a liquefied product containing liquefied natural gas and a heavy component of the feed gas are associated together; and determining, as one new operating condition, a composition of the mixed refrigerant that optimizes a production efficiency of the liquefied natural gas predicted by the training model (88) from a latest composition of the feed gas in the liquefied natural gas plant (2) and a latest ambient temperature.

A method for liquefying a stream of hydrocarbons from a feed stream, including introducing the feed stream and a first cooling stream into a first heat exchanger, extracting a plurality of partial cooling streams obtained from the first cooling stream from the heat exchanger via separate outlets, introducing each partial cooling stream into an expansion element to produce a plurality of biphasic cooling streams at different pressures, introducing each biphasic cooling stream into a phase separator element to produce a gaseous cooling stream which is diverted from the first exchanger and a liquid cooling stream which is introduced into the first exchanger via respective inlets, evaporating each liquid cooling stream by heat exchange with at least the feed stream and the first cooling stream so as to extract a cooled hydrocarbon stream at the outlet from the first heat exchanger and to extract a plurality of evaporated cooling streams.

A liquefaction system and method for producing liquefied natural gas (LNG) is provided. The liquefaction system may include a heat exchanger to cool natural gas to LNG, a first compressor to compress and combine first and second portions of a single mixed refrigerant from the heat exchanger, a first cooler to cool the single mixed refrigerant from the first compressor to a first liquid phase and a gaseous phase, and a first liquid separator to separate the first liquid phase from the gaseous phase. The liquefaction system may also include a second compressor to compress the gaseous phase, a second cooler to cool the compressed gaseous phase to a second liquid phase and the second portion of the single mixed refrigerant, a second liquid separator to separate the second liquid phase from the second portion of the single mixed refrigerant, and a pump to pressurize the first liquid phase.

A sinusoidal corrugated tube-type spiral wounded heat exchanger suitable for FLNG, wherein a top of an outer cylinder has a shell-side refrigerant inlet and a bottom thereof has a shell-side refrigerant outlet; a sinusoidal corrugated tube-type liquid distributor is below the shell-side refrigerant inlet, a first sinusoidal corrugated winding tube bundle and a second sinusoidal corrugated winding tube bundle, which are heat exchanger tubes with a sinusoidal wave shape, are inside the outer cylinder, and peaks and troughs of the first sinusoidal corrugated winding tube bundle and the second sinusoidal corrugated winding tube bundle are in staggered correspondence one by one from top to bottom; a sinusoidal corrugated tube-type liquid distributor includes a one-into-two-type tube, a two-into-four-type tube, two sinusoidal corrugated tube-type liquid distribution tubes from top to bottom.

A process for producing liquefied natural gas and liquid carbon dioxide comprising: Step a): separating a natural gas feed gas into a CO.sub.2-enriched gas stream and a CO.sub.2-depleted natural gas stream; Step b): liquefying the CO.sub.2-depleted natural gas stream in a liquefaction unit comprising at least a main heat exchanger and a system for producing frigories, said liquefaction unit comprising at least one refrigeration cycle fed by a refrigerant stream; Step c): simultaneous liquefying of the CO.sub.2-enriched gas stream resulting from step a) in a CO.sub.2 liquefaction unit; wherein the refrigeration necessary for the liquefaction of the CO.sub.2-enriched gas stream and for the liquefaction of the natural gas is supplied by said frigorie-producing system of the liquefaction unit and in that the refrigeration necessary for the liquefaction of the CO.sub.2-enriched gas stream originates from a portion of said refrigerant stream supplying the refrigeration cycle of said liquefaction unit.